Scanning electron microscopes (SEM) and focused ion beam (FIB) systems are available as the apparatuses that observe, measure, and/or process a sample using a beam of charged particles, such as an electron beam or an ion beam. These apparatuses irradiate the surface of a sample with a beam of charged particles, detect the secondary charged particles arising from the sample, and thus acquire a two-dimensional image signal representing the surface topography of the sample.
Irradiation with the beam of charged particles may generate a temporary positive or negative charge in the irradiated region of the sample due to a difference between the number of charged particles incident upon the sample and that of secondary charged particles released from the sample. The charge that the charged particle beam thus generates in the irradiated region is called a local charge, and this region covers a range of several hundreds of micrometers (μm) square.
Scanning the charged particle beam a plurality of times in this extremely small region increases an impact of the local charge upon the sample surface, thus causing astigmatism, changes in magnification, and other events.
A method of mounting an electron shower generating device and an ion shower generating device, as disclosed in Patent Document 1 listed below, exists as a way to resolve the problem of astigmatism and changes in magnification, caused by the local charge on the sample surface. In addition, Patent Document 2 listed below discloses, as a method of neutralizing both the above local charge and a global charge that occurs extensively on the sample, employing an electrode unit in which a charged particle beam source for local charge neutralizing, and a charged particle beam source for global charge neutralizing are equipped additionally.